Spacelabs Compatible Adult/Pediatric 3 Lead ECG Trunk Cable with Round, Dual Keyed 17-pin Connector. In stock. $72. 
Replacement: Cables and Sensors: TL-23960. AMC: CB-61396R. Curbell: CBT-03MC-10CT-0021. Sage: T03-03-30M. Schiller: 55.065081. Spacelabs: 012-0108-01, 700-0008-08.